Enanta Announces U.S. FDA Approval of AbbVie’s MAVYRET™ (glecaprevir/pibrentasvir) for the Treatment of Chronic Hepatitis C in All Major Genotypes (GT1-6) in as Little as 8 Weeks

MAVYRET is a new, 8-week, pan-genotypic treatment for hepatitis C
patients without cirrhosis and new to treatment

FDA approval is supported by an overall 98 percent cure rate (rates
ranged between 92-100 percent) in patients who received the
recommended duration of treatment

MAVYRET is approved for use across all stages of chronic kidney
disease in patients with any of the major HCV genotypes

MAVYRET may be used in up to 95 percent of HCV patients, depending
on stage of liver disease and prior treatment history*

Glecaprevir, one of the two new direct-acting antivirals (DAAs) in
MAVYRET, is Enanta’s second protease inhibitor being developed and
commercialized by AbbVie

WATERTOWN, Mass.--(BUSINESS WIRE)--Aug. 3, 2017--
Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA), a research and
development-focused biotechnology company dedicated to creating small
molecule drugs for viral infections and liver diseases, today announced
that the U.S. Food and Drug Administration (FDA) approved AbbVie’s
MAVYRET™ (glecaprevir/pibrentasvir), a once-daily, ribavirin-free
treatment for adults with chronic hepatitis C virus (HCV) infection
across all major genotypes (GT1-6). MAVYRET is an 8-week, pan-genotypic
treatment for patients without cirrhosis and new to treatment. Up to 95
percent of HCV patients in the U.S. may be eligible for treatment with
MAVYRET, including patients with compensated cirrhosis or without
cirrhosis, and those with limited treatment options, such as patients
with chronic kidney disease (CKD).*

Following this approval of MAVYRET in the U.S., Enanta expects to
receive a $40 million milestone payment from AbbVie.

“A majority of the estimated 3.4 million Americans chronically infected
with HCV have not yet been treated for the disease and do not yet have
cirrhosis. The FDA approval of MAVYRET provides them a new, 8-week
treatment option regardless of their HCV genotype,” stated Jay R. Luly,
Ph.D., President and CEO, Enanta. “Our second protease inhibitor,
glecaprevir, is part of this new combination treatment that has now been
approved in the E.U. and the U.S.”

Approximately 3.4 million Americans are chronically infected with HCV.1
Additionally, HCV is common among people with severe CKD, with
more than 500,000# people in the U.S. estimated to have both
chronic HCV and CKD.2 MAVYRET was designed to deliver a
cure** across all major genotypes and for specific treatment challenges,
such as patients with severe CKD, and GT1 patients not cured by a NS5A
inhibitor or a NS3/4A protease inhibitor (PI) in a direct-acting
antiviral (DAA) treatment, but not both. MAVYRET combines two new DAAs
that target and inhibit proteins essential for the replication of the
hepatitis C virus.

The approval of MAVYRET is supported by data from nine registrational
studies in AbbVie’s clinical development program, which evaluated more
than 2,300 patients in 27 countries across all major HCV genotypes
(GT1-6) and special populations.

AbbVie’s pan-genotypic regimen also was recently granted marketing
authorization by the European Commission, which means it is now licensed
for use in all 28 member states of the European Union, as well as
Iceland, Liechtenstein and Norway.

**Patients who achieve a sustained virologic response at 12 weeks post
treatment (SVR12) are considered cured of hepatitis C.

#Based on IMS Dx (Oct. 2016) distribution of 15.7% Renal
patients in diagnosed population applied to ~3.4M HCV prevalence
population of all major HCV genotypes

About MAVYRET™ (glecaprevir/pibrentasvir)

MAVYRET® is approved by the U.S. Food and Drug Administration (FDA) for
the treatment of chronic hepatitis C virus (HCV) infection in adults
across all major genotypes (GT1-6). MAVYRET is a pan-genotypic,
once-daily, ribavirin-free treatment that combines glecaprevir (100mg),
an NS3/4A protease inhibitor, and pibrentasvir (40mg), an NS5A
inhibitor, dosed once-daily as three oral tablets, taken with food.

MAVYRET is an 8-week, pan-genotypic option for patients without
cirrhosis and new to treatment, who comprise the majority of people
living with HCV. MAVYRET is also approved as a treatment for patients
with specific treatment challenges, including those (GT1) not cured by
priortreatment experience with either a protease inhibitor or an
NS5A inhibitor (but not both), and in patientswith limited
treatment options, such as those with severe chronic kidney disease
(CKD) or those with genotype 3 chronic HCV. MAVYRET is approved for use
in patients across all stages of CKD with any of the major HCV genotypes
(GT1-6).

USEMAVYRET™ (glecaprevir and pibrentasvir) tablets are a
prescription medicine used to treat adults with chronic (lasting a long
time) hepatitis C virus (hep C) genotypes 1, 2, 3, 4, 5, or 6 infection
without cirrhosis or with compensated cirrhosis.

IMPORTANT SAFETY INFORMATIONWhat is the most important
information to know about MAVYRET?

Hepatitis B virus reactivation: Before starting treatment with
MAVYRET, a doctor will do blood tests to check for hepatitis B virus
infection. If people have ever had hepatitis B virus infection, the
hepatitis B virus could become active again during or after treatment of
hepatitis C virus with MAVYRET. Hepatitis B virus becoming active again
(called reactivation) may cause serious liver problems including liver
failure and death. A doctor will monitor people if they are at risk for
hepatitis B virus reactivation during treatment and after they stop
taking MAVYRET.

MAVYRET must not be taken if people:

Have certain liver problems

Are taking the medicines:

atazanavir (Evotaz®, Reyataz®)

rifampin (Rifadin®, Rifamate®, Rifater®, Rimactane®)

What should people tell a doctor before taking MAVYRET?

If they have ever had hepatitis B virus infection, liver problems
other than hep C infection, or any other medical conditions.

If they are pregnant or plan to become pregnant, or if they are
breastfeeding or plan to breastfeed. It is not known if MAVYRET will
harm a person’s unborn baby or pass into breast milk. A doctor should
be consulted about the best way to feed a baby if taking MAVYRET.

About all the medicines they take, including prescription and
over-the-counter medicines, vitamins, and herbal supplements. MAVYRET
and other medicines may affect each other. This can cause people to have
too much or not enough MAVYRET or other medicines in their body. This
may affect the way MAVYRET or other medicines work, or may cause side
effects.

A new medicine must not be started without telling a doctor. A
doctor will provide instruction on whether it is safe to take MAVYRET
with other medicines.

What are the common side effects of MAVYRET?

The most common side effects of MAVYRET are headache and tiredness.

These are not all of the possible side effects of MAVYRET. A doctor
should be notified if there is any side effect that is bothersome or
that does not go away.

This is the most important information to know about MAVYRET. For
more information, people should talk to a doctor or healthcare provider.

People are encouraged to report negative side effects of prescription
drugs to the FDA. Visit www.fda.gov/medwatch
or call 1-800-FDA-1088.

Please see full Prescribing Information, including the Patient
Information.

If people cannot afford their medication, they should contact www.pparx.org
for assistance.

About EnantaEnanta Pharmaceuticals is a research and
development-focused biotechnology company that uses its robust
chemistry-driven approach and drug discovery capabilities to create
small molecule drugs for viral infections and liver diseases. Enanta’s
research and development efforts are currently focused on the following
disease targets: non-alcoholic steatohepatitis (NASH)/ primary biliary
cholangitis (PBC), respiratory syncytial virus (RSV) and hepatitis B
virus (HBV). Enanta has also discovered novel protease inhibitors that
have been developed as part of AbbVie’s hepatitis C virus (HCV)
treatment regimens under a collaboration that now provides Enanta a
payment stream, which it is using to fund its research and development
programs. Please visit www.enanta.com
for more information on Enanta’s programs and pipeline.

FORWARD LOOKING STATEMENTSThis press release contains
forward-looking statements, including statements with respect to the
prospects for commercialization of MAVYRET in the United States.
Statements that are not historical facts are based on management’s
current expectations, estimates, forecasts and projections about
Enanta’s business and the industry in which it operates and management’s
beliefs and assumptions. The statements contained in this release are
not guarantees of future performance and involve certain risks,
uncertainties and assumptions, which are difficult to predict.
Therefore, actual outcomes and results may differ materially from what
is expressed in such forward-looking statements. Important factors and
risks that may affect actual results include: the efforts of AbbVie (our
collaborator developing MAVYRET) to commercialize MAVYRET successfully
in the U.S. and to obtain regulatory approvals of the
glecaprevir/pibrentasvir (G/P) combination and commercialize it
successfully in other jurisdictions; the regulatory and marketing
efforts of others with respect to competitive treatment regimens for
HCV; regulatory and reimbursement actions affecting MAVYRET, any
competitive regimen, or both; the need to obtain and maintain patent
protection for glecaprevir and avoid potential infringement of the
intellectual property rights of others; and other risk factors described
or referred to in “Risk Factors” in Enanta’s most recent Form 10-K for
the fiscal year ended September 30, 2016 and other periodic reports
filed more recently with the Securities and Exchange Commission. Enanta
cautions investors not to place undue reliance on the forward-looking
statements contained in this release. These statements speak only as of
the date of this release, and Enanta undertakes no obligation to update
or revise these statements, except as may be required by law.